Topic 3 - DNA & Protein Synthesis

Question 1

Describe DNA

Answer 1

• Found in the nucleus
• Stands for deoxyribonucleic acid
• A polymer - made up of many nucleotides
• Contains genetic instructions for the coding of proteins
• Each nucleotide is consists of one sugar molecule, one phosphate molecule and one nitrogenous base
• In the shape of a double helix

Question 2

What is a gene?

Answer 2

A short section of DNA that codes for a protein

Question 3

What are the nitrogenous bases?

Answer 3

Adenine
Thymine
Cytosine
Guanine

Question 4

What nitrogenous base replaces the role of thymine in RNA

Answer 4

Uracil

Question 5

What type of bond is between complimentary bases

Answer 5

Hydrogen bond

Question 6

What are the complimentary bases

Answer 6

A-T
C-G

Question 7

What are the 2 stages of protein synthesis?

Answer 7

1. Transcription
2. Translation

Question 8

What happens during protein synthesis?

Answer 8

1. An enzyme called RNA polymerase binds to the non-coding DNA in front of a gene on the uncoiled DNA strand
2. The strands of DNA unzip, due to helicase enzymes breaking down hydrogen bonds , and the RNA polymerase cause mRNA nucleotides in the nucleus to match to their complimentary base on the DNA to form mRNA
3. The mRNA strand leaves the nucleus through pores in the nuclear membrane, into the cytoplasm and onto ribosomes
4. The mRNA provides a template for the sequence of amino acids in the protein being produced, as each triplet of bases (codon) matches to anti-codons on tRNA on amino acids
5. This results in a specific order of amino acids that fold into a specific shape and bond with peptide bonds, producing polypeptide.
6. The final result is a specific protein with a specific function and shape

Question 9

How would you extract DNA from a kiwi?

Answer 9

1. Peel the skin off of the kiwi and pulverise it to expose its cells and increase its surface area
2. Add it to a mixture of cold water, salt and detergent. The salt coagulates the DNA to increase its visibility and the detergent contains lipase to break down lipid-based cell membranes
3. Filture the solution with filter paper and pour the filtrate into a test tube
4. Add pineapple juice, which contains protease, to break down the histone proteins that hold DNA together to maintain the shape of chromsomes
5. Add ethanol, which causes the DNA to precipitate and float to the top of the solution, as a highly visible, jelly-like substance

Question 10

What is a chromosome?

Answer 10

A structure found in the nucleus, which is made up of a long strand of DNA